Predicting sedimentation from timber harvest areas with the WEPP model

Elliot, W.J.; Luce, C.H.; Robichaud, P.R. 1996. Predicting sedimentation from timber harvest areas with the WEPP model. In: Proceedings of the Sixth Federal Interagency Sedimentation Conference, March 1996, Las Vegas, NV. 8 p.

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Abstract: Disturbed forest lands are prone to increased erosion. Predicting the effects of forest operations on surface hydrology and erosion is difficult. Hydrologic models have been developed for agricultural conditions, but they may not be valid in forests. The WEPP model, a process-based erosion model under development, may have limitations in modeling erosion in forest areas. Field research has shown that timber harvest area soil properties may vary widely. Validation studies with the Watershed Version of the WEPP model show that as observed, snow melt dominates the runoff processes in the Northern Rockies, and that disturbed areas generally have a greater influence on runoff and erosion than do undisturbed areas. The model overpredicted snow melt rate, and did not allow snow to accumulate, but rather melted any accumulation on the first day that was above freezing following a snow event. It may be necessary to reduce hydraulic conductivities from those observed on small field plots to obtain runoff. A model that better describes the attributes of this region's snowmelt processes and upland hydrology is needed. Additional research is also needed for modeling the large spatial variability observed in timber harvest areas. Research is ongoing to address all of these forest-specific problems.

Moscow FSL publication no. 1996d